1. The Field of the Invention
The present invention relates to exercising equipment, in particular a weight lifting machine.
2. Description of Related Art
Lifting weights has been a historic method of building and toning body muscles. Over the years weight lifting machines have been developed to provide controlled lifting motions and to remove the bulkiness of "free style" weight lifting. A typical weight lifting machine utilizes cables and pulleys to convert human body movement into a vertical translation of weights.
U.S. Pat. No. 5,067,708 issued to Oschansky, discloses an exercise machine that incorporates three cables and a series of pulleys that vertically lift a weight stack in response to the angular displacement of an actuating arm. The Oschansky device includes a frame and an actuator arm assembly that can be adjusted to a number of positions along a vertical bar of the frame. The adjustment means allows the user to vary the height of the actuator arm.
The actuator arm of the Oschansky machine is attached to a cam that is coupled to a vertical translation plate by a pair of chains. The vertical translation plate is coupled to the weight stack by the cable/pulley assembly. The cable/pulley assembly has a pair of floating pulleys that move when the actuator arm assembly is adjusted so that slack is not created in the system. The pulleys do not displace vertically when the actuator arm is rotated during an exercise routine.
Rotation of the actuator arm and cam pulls the translation plate in a downward direction. Movement of the plate pulls the cables and lifts the weight stack. The chains are located off-center from the center line of the plate, so that rotation of the arm and cam in either direction causes one of the chains to pull the translation plate. Such an arrangement creates a torque on the plate. To compensate for the torque, the Oschansky device provides rollers that guide and secure the translation plate within a pair of grooves located in the frame of the machine. The rollers and guides create additional components that increase the complexity and cost of the machine. Additionally, because of the limitations of the plate/chain assembly, the actuator arm of the Oschansky machine cannot be rotated more than 180.degree.. It has been found that some users prefer rotating the arm more than 180.degree., especially if the user desires a certain amount of pretension in the arm. It would therefore be desirable to provide an exercise machine that provides greater than 180.degree. of rotation. It would also be desirable to have such a machine that allows the actuator arm to be vertically adjusted without effecting the range of rotation of the arm, or the cable tension in the system.